A single 0-100 number summarising how prepared you look for hard training today, built from recent sleep, heart rate variability, resting heart rate and recent training load. It is a starting point for a decision, not an instruction.
Each contributing factor carries its own sub-score, so you can see which one moved the total. When one factor is dragging the score down, that is usually more actionable than the headline number - a low score from one poor night means something different from a low score from three weeks of accumulated load.
The prescription is derived from the score and your recent training, not from a plan you agreed to. It is a default worth overriding when you know something the app does not - a stressful week, a race on the calendar, or simply feeling better than the number suggests.
Readiness is built from a wearable's estimates and can be wrong. If the number is low but you feel good, and nothing in your training history suggests fatigue, trust yourself. Persistent disagreement between how you feel and what the score says is worth investigating rather than ignoring.